"""
Date utilities for the owned clip analysis backfill job.

This module provides utilities for date range generation and date-based
processing logic for the backfill job.
"""

from datetime import datetime, timedelta
from typing import List, Generator


def generate_date_range(start_date: str, end_date: str, date_format: str = "%Y-%m-%d", reverse: bool = False) -> Generator[str, None, None]:
    """
    Generate a sequence of dates from start_date to end_date (inclusive).
    
    Args:
        start_date: Start date in YYYY-MM-DD format
        end_date: End date in YYYY-MM-DD format (inclusive)
        date_format: Date format for parsing and output
        reverse: If True, generate dates from end_date to start_date
        
    Yields:
        Date strings in the specified format
        
    Raises:
        ValueError: If date format is invalid or start_date > end_date
    """
    try:
        start_dt = datetime.strptime(start_date, date_format)
        end_dt = datetime.strptime(end_date, date_format)
        
        if start_dt > end_dt:
            raise ValueError(f"start_date ({start_date}) must be <= end_date ({end_date})")
        
        if reverse:
            # Generate dates from end_date backward to start_date
            current_dt = end_dt
            while current_dt >= start_dt:
                yield current_dt.strftime(date_format)
                current_dt -= timedelta(days=1)
        else:
            # Generate dates from start_date forward to end_date (original behavior)
            current_dt = start_dt
            while current_dt <= end_dt:
                yield current_dt.strftime(date_format)
                current_dt += timedelta(days=1)
            
    except ValueError as e:
        if "time data" in str(e):
            raise ValueError(f"Invalid date format. Expected {date_format}. Error: {e}")
        raise


def get_date_list(start_date: str, end_date: str, date_format: str = "%Y-%m-%d") -> List[str]:
    """
    Get a list of all dates from start_date to end_date (inclusive).
    
    Args:
        start_date: Start date in YYYY-MM-DD format
        end_date: End date in YYYY-MM-DD format (inclusive)
        date_format: Date format for parsing and output
        
    Returns:
        List of date strings in the specified format
        
    Raises:
        ValueError: If date format is invalid or start_date > end_date
    """
    return list(generate_date_range(start_date, end_date, date_format))


def get_next_date(date_str: str, date_format: str = "%Y-%m-%d") -> str:
    """
    Get the next date after the given date.
    
    Args:
        date_str: Date string in specified format
        date_format: Date format for parsing and output
        
    Returns:
        Next date string in the specified format
        
    Raises:
        ValueError: If date format is invalid
    """
    try:
        date_dt = datetime.strptime(date_str, date_format)
        next_dt = date_dt + timedelta(days=1)
        return next_dt.strftime(date_format)
    except ValueError as e:
        raise ValueError(f"Invalid date format. Expected {date_format}. Error: {e}")


def get_date_range_info(start_date: str, end_date: str, date_format: str = "%Y-%m-%d") -> dict:
    """
    Get information about a date range.
    
    Args:
        start_date: Start date in specified format
        end_date: End date in specified format
        date_format: Date format for parsing
        
    Returns:
        Dictionary with range information
        
    Raises:
        ValueError: If date format is invalid or start_date > end_date
    """
    try:
        start_dt = datetime.strptime(start_date, date_format)
        end_dt = datetime.strptime(end_date, date_format)
        
        if start_dt > end_dt:
            raise ValueError(f"start_date ({start_date}) must be <= end_date ({end_date})")
        
        total_days = (end_dt - start_dt).days + 1  # +1 to include end_date
        
        return {
            "start_date": start_date,
            "end_date": end_date,
            "total_days": total_days,
            "date_range_description": f"{start_date} to {end_date} ({total_days} days)"
        }
        
    except ValueError as e:
        if "time data" in str(e):
            raise ValueError(f"Invalid date format. Expected {date_format}. Error: {e}")
        raise